عنوان مقاله [English]
Nowadays, with development of subway tunnels, heating and cooling stations is playing an important role. Shallow geothermal energy as a renewable time-independent energy source has helped significantly to reduce energy consumption for supplying ventilation, heating, and cooling of subway stations. The amount of accessible energy from such modern system has great importance in their economic assessment. Hence, this research aims to perform and present a finite element modelling to evaluate the amount of exploited energy through ground heat exchangers (GHE) in tunnels. After validation of implemented modelling, the effect of various involved parameters in modelling was studied for a short-term operation of heat exchange. Additionally, the effect of lining isolation with respect to the inner environment of the tunnel was investigated. The results show that by increasing water velocity in the pipe, the total extracted power increased in both isolated and non-isolated conditions. The results could be classified into three main categories.
1. By increasing (a) the spacing between the pipe and inner environment of the tunnel in isolated case, (b) the inner temperature of the tunnel in non-isolated case, and (c) thermal conductivity of soil in both isolate and none-isolate cases, the total extracted power could be improved. The pipe diameter has a fascinating effect on the total extracted power. Firstly, it reduced the amount of extracted power. But, in larger diameters, due to capability of discharging more water, the amount of extracted power will be increased.
2. By increasing (a) the spacing between the pipe and inner environment of the tunnel in non-isolated condition and (b) pipe thickness in both non-isolated and isolated conditions, the total extracted power will be decreased.
3. By increasing the specific heat capacity, density, and porosity of the soil, the total extracted power slightly changes. Indeed, these parameters have a negligible effect on extracted power.